Incorporating finely divided particles during suspension polymerization



" United States atent amazes Patented May 11, 1965 3 183 208 INCORPORATING FnIELY DIVIDED murmurs DURING SUSPENSION POLYMERIZATION Hans Wolfgang Jurgeleit, Pittsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware No Drawing. Filed Aug. 22, 1961, Ser. No. 133,028 3 Claims. (Cl. 260-41) This invention relates generally to polymerization processes and more particularly to a polymerization process whereby finely divided particles of material, other than the polymer, are physically incorporated into the polymer.

One of the more important commercial methods for the production of polymers, such as, polystyrene and styrene copolymers, is suspension or bead polymerization. In this method, the polymerizable monomer is suspended in water, using as the suspension stabilizer a material such as calcium phosphate or polyvinyl alcohol, and polymerized with the aid of a catalyst. The suspension is heated to a temperature sufficient to activate the catalyst. The polymerization product is in the form of grains or beads on the order of 0.5 to 5 millimeters in diameter.

The industrial preference for suspension polymerization is obvious when one considers the rather high heat of polymerization of a monomer such as styrene which, using the suspension method, can be easily dissipated. Another advantage of the suspension process is that the granular product can be easily separated and can be further fabricated and handled with ease.

The beads obtained by suspension polymerization can be and often are further treated by mixing with other materials, such as, pigments, carbon black, etc. Generally, when the beads are to be mixed with another material, the mixing is done by dry-blending, i.e., a tumbling together of beads and additive, to give a reasonably homogeneous mixture of polymer and additive. In cases where it is imperative that the mixture of beads and additive be homogenous, the mixing is accomplished by the more expensive extrusion of the additive and polymer. Both of these mixing processes are time consuming and expensive. It would obviously be advantageous if the beads could be prepared so that, at the completion of the polymerization step, they already contain the additive, such as, a color or pigment, homogenously incorporated therein. The economic advantage of such a step is self-evident.

Materials, which it would be advantageous to incorporate into the polymer, include for instance, bentonite powder, which, according to United States Patent 2,921,042, improves the dyeing properties. Another desirable addition would be the incorporation of powders into polymers which are going to be further fabricated to prepare foamed plastics. It has been reported in the Society of Plastic Engineers Journal, July 1960, pages 705-709, that an improved cell structure is obtained by adding finely dispersed powders which act as nucleating agents during the foaming process. Another advantageous material to incorporate into the polymer would be a pigment to color the plastic. Still other additives would be those which would impart some degree of fire retardancy.

The foregoing materials are of an extremely fine particle size on the order of 0.01 to 100 microns. Additions of these materials have heretofore been made only by extrusion processes because the powdered form is so fine that a dry-blending process would not result in a blend of the required uniformity. Thus, these materials all must be made by extrusion. Unfortunate, even when mixed by an extruder, one pass through the extruder is not always sufiicient to obtain a homogeneous distribution of the powder and the plastic material, and often the material must be passed through the extruder two or more times.

. O This extrusion, step although laborous and expensive, 7

has been heretofore the only workable way for incorporating these fine powders into polymers which have been produced by the suspension polymerization method. As would be expected, because of the obvious attendant economic advantages, numerous attempts have been made to add various powders to the suspension polymerization with the hope that these powders would be occluded into the beads during the polymerization process. Unfortunately, however, such process have not been successful. One reason for this nonsuccess is that many of the powders are hydrophilic and although they are not soluble in water, they tend to remain in the water phase to the exclusion of the organic phase. Other of these fine powders, although not hydrophilic, will accumulate in an interlayer between the water phase and the organic phase and act as a suspending agent for the monomer without intruding into the monomer phase. This is, of course, the function of suspending agents in the suspension polymerization process. An example of the former material is sodium bicarbonate, while an example of the latter is finely divided talc such as is used as a suspending agent in the suspension process.

I have now discovered a method wherein it is possible to homogeneously incorporate finely divided solid foreign substances into the beads produced by the suspension polymerization process during the polymerization of the beads. This novel process eliminates the need for any after-mixing of polymer and additive by extrusion or by any other method.

My novel process for the production of beads which contain, homogeneously occluded therein, finely divided foreign substances, contemplates an initial polymerization of at least 30% but less than of a vinyl monomer followed by the addition of finely divided foreign substance, the subsequent establishment of an aqueous suspension of the foreign substance containing partially polymerized monomer, and finally the substantial completion of polymerization.

The first stage of the polymerization may be carried out in bulk or in the presence of water. The presence of water is advantageous in that it helps to dissipate the heat of reaction. This advantage of heat dissipation, however, requires that certain precautions be observed in order to avoid other undesirable effects. For example, if the first part of the polymerization is carried out in the presence of water, the possibility exists that the powder to be incorporated may act as a suspending agent for the monomer being polymerized. If this occurs, the powder cannot be incorporated into the polymer. This undesirable possibility is avoided if the powder is added after polymerization has partially proceeded. The point the polymerization should reach prior to addition is that point where the partially polymerized monomer has ag: glomerated in the form of a viscous mass. This point occurs after at least 30% of the monomer has been converted to polymer. The polymerization should have proceeded so far as not to permit the partially polymerized monomer to form a suspension on the addition of the powder. The establishment of a suspension may be recognized by the formation of discrete droplets of monomer in the water. If the powder is added after the monomer has agglomerated into a viscous mass, initially the powder will be found both in the water and the monomer. However, with continued agitation, the partially polymerized monomer soon contains all of the powder and the water phase becomes perfectly clear.

The degree of polymerization is related to the viscosity of the polmerizing monomer. For instance, the maximum degree of polymerization which can be tolerated prior to the addition of the additive is about 85 The viscosity of the polymerizing monomer can be measured with a Gardner Bubble Viscometer and the degree of polymerization determined therefrom. It has been found, for instance, that if the polymerizing monomer is styrene, 85% polymerization corresponds to a Gardner viscosity of approximately Z8 to 9, determined at 25 C. The viscosity terns are discussed, for example, in Styrene, Its Polymers, Copolymers and Derivatives, Boundy'Boyer, Reinhold Publishing Corporation, 1952, page 241, et seq.

After establishment of the suspension, the polymerizaof other partially polymerized monomers may also be tion is carried out in the usual way by continued heating. related to the degree of polymerization by standard proc- The process of suspension polymerization is well known esses so that this degree of polymerization can readily be and is described, for example, in U.S. Patents 2,656,334 determined from the viscosity. and 2,692,251, as well as in Styrene, Its Polymers, Copoly- Another danger which exists if the initial polymerizamers and Derivatives, Boundy-Boyer, Reinhold Publishtion is carried out in water is that an emulsion may be 1() ing Corporation. 1952, page 286, et seq. formed. The formation of an emulsion can be prevented The beads so produced may be further processed; parin several ways. One of the most common methods is to ticularly, they may be rendered expandable. This is acadd a salt such as, for example, postassium bromide or complished by adding a normally liquid hydrocarbon to a sodium chloride. suspension of beads under pressure. The hydrocarbon is Salts which may be used to prevent an emulsion are forced into the beads which then can be expanded by the those neutral inorganic salts which are not peptizing agents application of heat. Such process is described in U.S. and which further do not interfere with the polymeriza- Patent 2,983,692, Gaetano F. DAlelio, assigned to the tion. Suitable salts which meet these criteria are: sodium assignee of the present application. chloride, potassium chloride, sodium nitrate and potassium The following examples more fully illustrate the pracsulfate. Salts which cannot be used because they tend to tice 0f the invention: act as stabilizers are the phosphates. Salts which cannot Example 1 3; gg si gfifi 3 5; 3: 2 gg ggg are 5k two-liger Pyrex glass reaction kettle, equipped with a If the first part of the polymerization is carried out in gas; :2: z is g f zfi gg gi z g' T-shapec; wfater, andla salt is added initially to prevent the formation sodium chloride i a solution z g i g i gigi g 0 an emu sion, some of the elow-mentioned suspending agentslor thickeners may coagulate. This will happen, for 18,33 5 g g gg g g figi i gi z az g igg fi gz examp c, with sodium chloride as the salt and l in l alcohol as the thickener. It will be easy for those; s lc ill d fon-nanon of an emulslon and the benz9yl Peroxide and tertiary butyl perbenzoate are polymerization catalysts. In the technique of suspension polymenzatlon to avoid Th k ttl d h 0 these difficulties by proper choice of reactants. C e 3- e was insane 111-an O1 at and heated t9 90 If the first stage of polymerization has been carried out w ehagltatmn wa bemg earned A disperin the presence of sufficient water, the only addition which sion 9 t e mot-mm?!- m-water was created'- T-hls disperneed be made after the powder which is to be incorporated slog-mcre-ascd m vlscoslty eventually lost its identity as is added, is that of suspending agent and if desired, polym- 3 i 3:53? g f 8 a vlsgous erization catalyst. If the initial polymerization has been t a ter a out 3 ours at 90 carried out in bulk or in the presence of insufficient water, a me a out 5% of the mopomer hai-i beqn additional water to insure suspension of the monomer comgertef to polymer 20 grains imnmony music m must be added to the suspending agent and catalyst. ga er a was added while Sui-ring was commued' The maximum amount of monomer to water is about 40 pow er absm:bed vlscous layer a re- 55 Parts monomer to parts of water. With more than fi with contlnued-S-mrmg 10d-ged At this amount of monomer, a stable suspension cannot be 3 our g of antlmony 4 the maintained. From an economic point of view, it is desiru pen mg agent m of 81 2% aquaous solution of hydroxyethyl cellulose (Celloslze WP-300) was added able that production be as close to this limit as possible mere t u d b because the process becomes progressively uneconomical 45 or a d -1 ifis: teak-up of viscous the further from the maximum you go. From a practical folgm 8 a i g a suspelislon m the standpoint, the minimum amount of monomer is about 20 met in the e 1 e g y polymimzcd mono Part5 P 45 Parts of mommertinued at 90 so th a t t h e fot'ril 20 13223 2 3: ii mi zit Any of the well-known suspending agents or thlckeners this temperature was 7% hours. Thereafter, the polymy be used, example, carbohydrates, -8-, r erization vessel was closed and polymerization was conpectin, plant gums, etc., proteinaceous materials, e.g., gelatinued for another 6 hours at a temperature of 115 C tin and glue, modified celluloses, e.g., methyl cellulose Polymerization was discontinued. The beads formed were hydroxyethyl cellulose, carboxymethyl cellulose and its separated, washed and dried. Analysis showed that they salts, etc., synthetic polymeric agents such as polyvinyl contained 1.58% antimony oxide. Bead size distribution alcohol, salts ofpolyacryl1c or polymethacrylic acids, polywas determined using a standard Ro-Tap machine and methacrylamlde, polyvinyl pyrrolidone, etc. The amount the following bead size distribution was obtained:

Bead diameter 2 mm. 0.84 mm. 0.59mm. 0.42 mm. 0.42 mm.

Us Standard Stoves... On 10"... On 20 On 30..... On 40. Thru 40 mesh Beaddistrlbution 64.7%..- 30.6%..-" 2.6% 1.2% asigf gt suspending agent varies with the particular system used Example 2 ut is easi y ascertainable by experimentation.

If the first part of the Polymerization is carried out in ga a kettlle 9 the type used Exampie 1 was the absence of water, the powder to be incorporated may f z f sofunon of 600 grams of potassmm be added at any point up to that point where a stable susg m 0 water Thcreaftqr 200 grams of 3 pension is established by the addition of suflicient water romldc, was added i heated f and suspending agent to establish it, e.g., a Gardner vit at only a mmor Porno 0f thc sodium cosity of L9 determined at 70 bromide was dissolved. The purpose of the potassium Gena-any, a catalyst is added to increase the rate f bromide is to prevent the formation of an emulsion, while polymerization. Any of the common polymerization catthc Sodium bromide is incorporated into the P y to alystgmay be used For example, a mixturc of benzoyl impart fil'fl retardence thereto. There was then added a peroxide and tertiary butyl perbenzoate or ditertiary butyl solution of 1 gram of benzoyl peroxide and 0.25 gram perbenzoate may be used. Other applicable catalyst sysof tertiary butyl perbenzoate in 500 grams of styrene.

6 Stirring was continued and the temperature raised to 90 Example 4 C. in order to disperse the styrene monomer in the water. A resin kettle f the t e described in Exam 1e 1 was After about 31/2 hours at F about 70% Conversion charged with 400 m1. of ii ate'r and 160 grams (Ff sodium of monomer to p y the disperswn of the styrene was chloride. This was heated to 70* c. A solution of 1.0

st and a Viseoue i y i layer 5 grams of dibenzoyl peroxide and 0.25 gram of tertiary embed F of the Sedlllm bromlde POWder Whleh e? not butyl perbenzoate in 400 grams of styrene monomer was been dlssolved in the water phase. After an additional added, while stirring at a speed of 404 The hour's heailhg at 150 of a 2% aqueous perature was raised to 90 C. and maintained for 4 /2 droxyethyl cellulose solution were added. This caused hours a conversion of about 30% h monomer h d the breakdown of the organic mass and the formation of 10 agglomerated i a continuous viscous l Tw h Suspension of monomer in Water- Heating was grams of Heliogen Blue K Toner 56-4107 was added to tlnued at 90 C- fo 41/2 hours to dlselete beadsthe reaction vessel, while heating and stirring continued.

In O d r to Carry out further p s the beads were The pigment was soon entirely occluded within the monoremoved from the reaction kettle and placed in 300 ml. mer phase i h none left i h t Th fte a beverage fl These homes were Sealed, Placed in an solution of 12 grams of hydroxyethyl cellulose in 600 ml. oil bath and heated at While y Were rotated of water was charged to the reaction kettle in order to 6 hours to Complete Polymerization In Order to P establish a suspension of the styrene in water. Polymeriduee expandable Polystyrene, the bottles Were then Opened zation was continued at 90 C. with stirring for a period and e c Was Charged Withv 6 grams of tfiealehll'h P of 8 /2 hours. The beads produced were of a homogenephat 0.5 gr Nacconol NRSF (sodium alkyl y ously dark blue color. The bead size distribution was fonate) and 9% by weight of the beads of normal pendetermined as in Example 1 and was found to be as tane. The bottles were rescaled, heated to 100 C. and follows: i

Bead diameter 2 min. I 084 mm. I 059 mm. 0.42 m. l 0.42 mm.

US Standard Sievcs... On 10.. On 20. On On Thrll 40 mesh Bead distribution 01.6%.-. 35.7%..-. 2.5% 0.3% c

rotated for another 4 hours. At the end of this period, Example 5 impregnation e complete; e heads thus ebtelned In order to demonstrate that the time at which the Were Washed W h Water, aeldlfied Water, and f powder to be incorporated into the polymer is of vital Water agalhsahd finally dfled The heads eontalhed w importance, a series of experiments were run, wherein 6. bromlne: predomlnahfly 1n the form 0f NaBr- The the addition was made at distinct times. In each case, a size distribution of the beads was as follows: charge of 500 ml. of water, 200 grams of sodium chloride,

Bead diameter "I 4.76 mm. 2.0 mm. 084 mm. 059 mm. I 0.59 mm.

US Standard Sieves. On 4 On 10 On 20 On 30"... Thru 30 mesh screen.

Bead distribution 8.0% 56.7% 30.6%-.- 2.6% 2.1%.

The beads were expanded by heating in steam for three 500 grams of styrene, 1 gram of dibenzoyl peroxide and minutes. The pre-expanded material was molded under a 025 gram of tertiary butyl perbenzoate was made to a steam pressure of 1 atm. (15 p. s.i.g.) to a polystyrene reactor of the type described in 'Example 1. In each infoam of a 17.6 g./liter weight (:density of 1.1 lbs/cu. stance, the resulting solution was heated to 90 C. with ft.). By analysis, the bromine content in this foam was stirring. The suspension was established using a 2% found to be 4.8%, most of which was present in the aqueous solution of hydroxyethyl cellulose. In the first form of NaBr. run, the powder to be incorporated was added simul- Example 3 taneously with the establishment of the suspension. In

the second run, the powder was added and thereafter the suspension was established. In the third run, the suspension was first established and then the powder added.

A resin kettle as the type used in Example 1 was charged with the solution of 0.25 gram of tertiary butyl perbenzoate and 1.0 gram of dibenzoyl peroxide and 400 grams of styrene. The solution was heated to 90 C.

with stirring. After a half-hour at 90 0., about 25% anna fiifii conversion, 3 grams of Red Lake CL-20-5200 was added. Experiment Color nrnn Heating was continued for an additional 2 hours at Gramsv Added Grams Added beads which time an aqueous solution of 8 grams of hydroxyafterafterethyl cellulose in 700 ml. of water was added to establish the suspension. Heating was continued until the hard beads-were obtained. This occurred after 8 /2 hours. At this time, the water phase was found to be substant y Colorless, all Of e f been lodged wlfhlh The results given in the table indicate clearly that in the beads. The bead size distribution was determined rder to get a homogeneous distribution of the powder as in Example 1 and found to be: within the polymer, the powder must be added prior to Bead diameter 2 mm. 084 mm. 0.59 mm. 042 mm. 0.42 mm.

US Standard Sieves... On 10 On 20... On 30"... On 40... Thru 40 mesh Bead distribution 11.7%--.- 82.4%-.." 4.4% 1.1% 0.35

the establishment of the suspension. If the powder is bead size distribution was performed as in Example l'and added at the same time the suspension is established, only the beads had the following distribution:

Bead diameter l 2 mm. 0.04mm. 059 mm. 0.42 0.42 mm.

US Standard Sieves... On 10. On 20.... On 30. On 40..." Thru 40 mesh Bead distribution 2.5% 45.0%-.-" 25.2%.--" 14.3%"... 135%? part of the powder will be occluded. Whereas, if the 1 The above example is indicative of the fact that it is not suspension is established prior to the addition of the necessary that the initial polymerization be carried out in powder, no occlusion at all will occur. the presence of water but that an initial bulk polymeriza- In each instance, the polymerization was carried out tion may be suspended with excellent results. for 9 hours beyond that shown in the table. Example 8 Example 6 15 Example 7 was repeated with the exception that 3 grams A series of four polymerizations were carried out in of Permanent Carmine FR Toner 35-5001 was substituted resin kettles such as described in Example 1. To each for the -25 grams of sodium bicarbonate used in Example kettle, there was charged 500 ml. of water, a solution of 7 and the first stage of polymerization was carried out for 1 gram of dibenzoyl peroxide and 0.25 gram of tertiary '3 rather than 4 hours. Homogeneously dark red heads butyl perbenozate in 500 grams of styrene monomer. To were produced. These beads had a particle size distribu- Kettles 1 and 2, there was also added 200 grams of sodium tion as follows:

Bead diameter "l 2 mm. 084 mm. 059 mm. 0.42 mm. 0.42 mm.

US Standard sieves... On On On 30... On 40-.." Thru 40 mesh S 11. Bead distribution 3.0% 96.3%..." 0.5% 0.1% 01 chloride. In each instance, polymerization was carried 3 Example 9 out by heating to 90 C. while stirring. After 3 hours at 0 A d o a ry glass hned 35-hter reactor equipped with stirrer, a? i gg i was g fi to about 65 and steam jacket, thermowell bafile, was charged with 8 kiloe 0 Owing a 1 were ma grams of styrene, 16 grams of dibenzoyl peroxide and 4 T0 Kettle grams of an ethoxylated Starch grams of tertiary butyl perbenzoate. The mixture was To Kettle 2-50 grams of a crude corn starch To Kettle 3 grams of an thoxylated starch agitated and after ten minutes, 160 grams of Red Lake CL-20-5200 was added. The reactor was heated to 90 T0 Kettle grams Of a crude com Starch C. for 3 hours. There was then added 120 grams of hy- In each instance, the starch was picked up rapidly by the droxyethyl cellulose in =14 liters of water. This was sufiimonomer phase, leaving the water phase clear. Upon cient to form a bead suspension of the polymerizing styrene absorption of the starch by the monomer phase, the temin the water hydroxyethyl cellulose mixture. Heating was perature was again raised to 90 C. over approximately continued for another 3 hours at 90 C. at which time the 4 hour. After an additional hour at this temperature, reactor was closed. At this point, 1.2 liters of a 1:1 mix- 650 ml. of a 2% aqueous hydroxyethyl cellulose solution ture of normal and isopentane was pressured into the was added to Kettles 1, 3 and 4, while 400 ml. of this soluclosed reactor. The temperature was held at 90 C. for a tion were added to Kettle 2. In each instance, this was total of 8 hours. After this, the temperature was raised sufiicient hydroxyethyl cellulose to establish a suspension. to 1 15 C. and held for 5 hours. The pressure was main- In all instances, polymerization was completed by heating tained throughout at 66 to 68 p.s.i.g. The reactor was then to 90 C. for a total of about 9 hours. At the completion cooled down to room temperature. The beads were reof polymerization, the beads were recovered, washed, covered, washed dried. The beads were of a deep red rinsed and dried. The beads from Kettles 1 and 3 were color and contained 6.3% pentane. Seventy-five percent white, while those from 2 and 4 were brownish due to the of the beads had a diameter of 2 to 4 mm. The portion brown color of the starch used. No starch was detectable of the beads were heated in steam at 100 C. for 3 to 4 in the at phase f any f th f r k tt1 minutes to give partially expanded beads having a density Example 6 was repeated except that the temperature was of 16 grams per liter, about one pound per cubic foot. not decreased to 65 C. when the starch additions were These beads were then molded into a 30 centimeter x 30 made. As a result, the starch swelled to give a syrup which centimeter x 30 centimeter foam block using pressurized dispersed the polymerizing mass in the water. As a result, Steam at 20 P- -S- no starch was occluded in the styrene phase, It is to be noted in contrast to Example 7 above, that in Example 7 this instance, the water suspending agent was added to the styrene rather than the styrene to the water. The order in A resin kettle of the type used in Example 1 was charged 0 which this is done is thus shown to be immaterial.

with a solution of 0.8 gram of debenzoyl peroxide and 0.2 Exam 1e 10 gram of tertiary butyl perbenzoate in 400 grams of p styrene. To this solution, there was added 2.5 grams of A solution of 1 gram of benzoyl peroxide, 0.25 gram finely divided sodium bicarbonate. Heating to 90 C. was f tia y yl p r nz ate in 500 grams of styrene was accomplished and the solution was held at this temperature added to a polymerization kettle of the type described in for 4 hours while undergoing stirring. By this time, the Example 1, wh ch kettle contained 500 m1. of water. There styrene was transformed into a viscous syrup in which the was thereafter added 200 grams of sodium chloride. This sodium bicarbonate was finely dispersed. The syrup was mixture was heated for 3% hours at 90 C. There was then transferred to another resin kettle which contained then added 20 grams of potassium fiuoroborate, which had the solution of 4 grams of hydroxyethyl cellulose and 600 been ground to a fine power. The potassium fluoroborate ml. of water, which had been preheated to 90 C. The was coated with 0.2% by weight ammonium stearate so syrup was added to this solution and a stable suspension that the potassium fluoroborate would not stick and coaguresulted. Polymerization was then continued for a time late in the presence of water. The potassium fluoroborate sufficient to result in hard beads. The sodium bicarbonate only partially dissolved in the water. The remainder was was homogeneously contained throughout the beads. The rapidly picked up by the polymerizing mass. Within 15 9 minutes, the water phase was perfectly clear and there was added 200 ml. of a hot, 2% aqueous solution of hydroxyethyl cellulose. Polymerization was continued by heating at 90 C. for a total of 9 hours. The polymerization of the charge of the kettle was then transferred to 300 10 methyl methacrylate. This mixture was heated at 85 C. while stirring at a speed of '400 r.p.m. After one hour's heating at 85 C., the partially polymerized methyl methacrylate formed a continuous viscous layer floating on top 5 of the water. At this time, 4 grams of Red Lake CL-20- ml. crown capped bottles and polymerization was com- 5200 was added to the kettle. This color pigment was pleted in the bottles by heating them at 115 C. for anabsorbed by the partially polymerized monomer in about other 6 hours. Flat, oblong beads were obtained, having one minute, leaving no pigment in the water. Heating the following bead size distribution: and stirring was continued for another minutes after Bead diameter 416 mm. I 3.36mm.l 2.0 mm. 084 mm. I 0.B4 mm. US BtandardSleves.... 0n4 Onti On 10".-- 0n20..-. Thrumesh screen. Beaddistribution 1.5% 6.0% 80.9%".-. 17.7%... 0.0%.

' The beads were recovered, washed and then charged into 300 ml. bottles, each bottle containing 60 grams of beads, 150 ml. of water, 60 mg. of Nacconol NRSF (sodium alkyl aryl sulfonate), 6 grams of zinc oxide and 9 ml. of normalpentane. The bottles were then sealed with crown caps and heated in an oil bath at 100 C. for 4 hours, while under- Bead diameter 2 mm. 084 mm. 059 mm. 042 mm. 0.42 mm.

US Standard Sieves... On 10... On 20... On On 40... Thru 40 mesh screen.

Bead distribution-.... 42.9%..." 48.9%-.." 5.3% 2.3% 0.6%.

going rotation. At the completion of this time, the beads 30 were recovered, washed and dried. They were found to have a pentane content of about 6.7% and were expanded into a foam having a density of one pound per cubic foot. Chemical analysis showed that 9.4% potassium fluoroborate was contained in the foam.

Example 11 Two resin kettles of the type described in Example 1 were each charged with 350 ml. of water and 150 grams of sodium chloride. A solution of 1.2 grams of dibenzoyl peroxide and 0.3 gram of tertiary butyl perbenzoate in 600 grams of styrene monomer was added to one kettle, A, while a solution of 1.1 grams of dibenzoyl peroxide and 0.28 gram of tertiary butyl perbenzoate in 500 grams of styrene monomer was added to the other kettle, B. The kettle contents were heated at 90 C. with stirring. After 3 hours at 90 C., correspondingto a conversion of about 65%, 4 grams of Red Lake CL-20-5200 was added to each reaction vessel, while heating and stirring continued. The pigment was soon entirely occluded within the monomer phase with none left in the water. After one-half hour, a hot solution of 3 grams of hydroxyethyl cellulose in 150 ml. of water was charged to each of the reaction kettles in order to establish a suspension of the polymerizing styrene in water. Polymerization was continued at 90 C., with stirring, for a period of 11 hours. The beads produced were of a homogeneously red color. The head size distribution was determined as in Example 1 and was found to be as follows:

In addition to styrene, styrene derivatives such as, dichlorostyrene and alphamethyl styrene may also be polyemrized' according to the above process. Additionally, other monomeric substances polymerizable by the suspension process such as acrylic and methacrylic esters, itaconic acid and its esters, fumaric and maleic esters, and mixtures of two or more of these monomers, as well as combinations of any of these above previously named monomers, with less than 50% by weight of other comonomers polymerizable under the suspension conditions, such as acrylic acid and acrylonitrile may also be copolymerized according to the process of the invention.

In addition to the materials above described in the examples, there may be incorporated into the polymerizing polymer, according to the process of the present invention, a great variety of other finely divided solid materials; for instance, inorganic insoluble materials such as fullers earth, bentonite, magnesium silicate, calcium carbonate, calcium phosphate, etc., inorganic color pigments such as titanium dioxide, zinc oxide, iron oxide, chromium yellow, ultramarine blue, aluminum bronze, etc. Also water soluble salts, either inorganic or organic, may be incorporated by adding them in the form of a fine powder to the monomer and carrying out the first part of the polymerization in bulk. In grinding up these salts to powders, it may be helpful to add minor amounts of materials such as ammonium stearate which prevent agglomeration and at the same time are helpful in dispersing the salt in the monomer. Water soluble inorganic salts which may be incorporated by this manner are sodium Bead diameter 2 mm. 0.84mm. 059 mm. 042 mm 0.42 mm.

US Standard sieves... On 10 On 20... On30... 0n40.... Thrummesh screen.

arm-rm A Bead distribution 2.4% 95.0% 1.5% 0.5% 0.0%.

KETTLE a Bead distribution..... 1.4% 82.7%"-.. 14.1%. 0.6% 1.2%.

Example 12 chloride, sodium bromide, sodium carbonate, potassium A resin kettle as described in Example No. 1 was charged with 600 ml. of water, 180 grams of sodium chloride and a solution of 0.6 gram dibenzoyl peroxide and 0.15 gram of tertiary butyl perbenzoate in 300 grams bicarbonate, sodium sulfate, etc. Also, there may be included organic compounds which are insoluble in styrene. Examples of these materials are highly chlorinated hydrocarbons, phthalocyanine pigments, color toners and 1 1 lakes, i.e., organic pigment precipitated on an absorptive or reactive substratum.

The foregoing has described a novel process for the incorporation of foreign substances into polymerizing monomer by dispersing the powder in a partially polymerized monomer and thenecreating a suspension of the partially polymerized monomer and finishing the polymerization by this suspension process.

I claim:

1. A process for homogeneously incorporating finely divided solid substances in beads of normally solid vinyl polymers comprising:

(a) partially polymerizing a vinyl monomer selected from the group consisting of styrene monomer and acrylic monomer to convert at least 30 but not more than 85 percent of said monomer to polymer,

(b) incorporating an inert finely divided solid substance in said partially polymerized monomer,

(c) forming an aqueous suspension of said partially polymerized monomer having said finely divided substance incorporated therein, and

(d) substantially completing the polymerization of said suspended partially polymerized monomer.

2. A process for making colored polystyrene beads comprising partially polymerizing styrene monomer dispersed in an aqueous medium in the absence of suspending agent to convert from 30 to 85 percent of said styrene to the polymer, physically incorporating an inert finely divided solid pigment into said partially polymerized styrene, forming an aqueous suspension of said partially polymerized styrene having said pigment incorporated therein, and substantially completing the polymerization of said partially polymerized styrene to form colored beads.

3. A process for making colored expandable polystyrene beads comprising partially polymerizing styrene monomer dispersed in an aqueous medium in the absence of suspending agent to convert from 30 to 85 percent of said styrene to the polymer, physically incorporating an inert finely divided solid pigment into said partially polymerized styrene, forming an aqueous suspension of said partially polymerized styrene having said pigment incorporated therein, substantially completing the polymerization of said partially polymerized styrene to form colored beads, and introducing into said colored beads a normally liquid blowing agent.

References Cited by the Examiner UNITED STATES PATENTS 2,489,226 11/49 Morris et al. 260-41 2,512,697 6/50 Te Grotenhuis 260-415 2,751,369 6/56 Te Grotenhuis 26041 2,848,428 8/58 Rubens 260-2.5 2,986,547 4/61 Jefts 260-41 MORRIS LIEBMAN, Primary Examiner.

LEON I. BERCOVITZ, Examiner. 

1. A PROCESS FOR HOMOGENEOUSLY INCORPORATING FINELY DIVIDED SOLID SUBSTANCES IN BEADS OF NORMALLY SOLID VINYL POLYMERS COMPRISING: (A) PARTIALLY POLYMERIZING A VINYL MONOMER SELECTED FROM THE GROUP CONSISTING OF STYRENE MONOMER AND ACRYLIC MONOMER TO CONVERT AT LEAST 30 BUT NOT MORE THAN 85 PERCENT OF SAID MONOMER TO POLYMER, (B) INCORPORATING AN INERT FINELY DIVIDED SOLID SUBSTANCE IN SAID PARTIALLY POLYMERIZED MONOMER, (C) FORMING AN AQUEOUS SUSPENSION OF SAID PARTIALLY POLYMERIZED MNOMER HAVING SAID FINELY DIVED SUBSTANCE INCORPORATED THEREIN, AND (D) SUBSTANTIALLY COMPLETING THE POLYMERIZATION OF SAID SUSPENDED PARTIALLY POLYMERIZED MONOMER. 